The pathogenesis of ulcerative colitis (UC) and Crohn's disease (CD) has been the focus of an intense research effort to improve diagnostic accuracy, shorten the time to confirmed diagnosis, identify new therapeutic agents, and predict responses to therapeutic agents. Inflammatory bowel disease (IBD) continues to present monumental challenges to the basic understanding of the onset and control of inflammatory processes. However, the new science of microarray gene expression profiling provides an incomparably powerful technique to 1. identify the molecular participants of the inflammatory process and 2. differentiate the mechanisms of these IBD diseases at the molecular level. Microarray technology allows the simultaneous study of thousands of expressed genes and the comparison of diseased versus control gene expression profiles. The goal of this project is to apply microarray gene expression technology to patient matched peripheral blood and biopsy samples and directly compare over-expressed and under-expressed genes in CD and UC versus non-IBD controls. From the thousands of genes studied, this project seeks to identify a very small number of genes (a Focused Gene Expression Profile) that will allow development of an accurate, non-invasive blood test for IBD diagnosis and definitive stratification of Crohn's disease and ulcerative colitis.